Embodiments of the present invention relate to a sputtering target for a sputtering chamber used to process a substrate.
A sputtering chamber is used to sputter deposit material onto a substrate in the fabrication of integrated circuits and displays. Typically, the sputtering chamber comprises an enclosure around a sputtering target facing a substrate support, a process zone into which a process gas is introduced, a gas energizer to energize the process gas, and an exhaust port to exhaust and control the pressure of the process gas in the chamber. The sputtering target is bombarded by energetic ions formed in the energized gas causing material to be knocked off the target and deposited as a film on the substrate. The sputtered material can be a metal, such as for example aluminum, copper, tungsten, titanium, cobalt, nickel or tantalum; or a metal compound, such as for example, tantalum nitride, tungsten nitride or titanium nitride.
In certain sputtering processes, a magnetic field generator provides a shaped magnetic field about the sputtering surface of the target to improve sputtering properties and the sputtering surface of the target. For example, in magnetron sputtering, a set of rotatable magnets rotate behind the sputtering targets to produce a magnetic field about the front surface of the target. The rotating magnetic field provides improved sputtering by controlling the rate of sputtering across the sputtering target.
A cooling system passes heat transfer fluid through a housing surrounding the rotatable magnets to cool the magnets and, more importantly, the underlying sputtering target. However, conventional cooling systems often fail to remove sufficiently high levels of heat from the sputtering target and/or fail to provide spatially uniform heat removal from the target. As a result, hotter regions of the sputtering target are often sputtered at higher sputtering rates than adjacent regions, resulting in uneven sputtering across the target surface. Uneven target sputtering in combination with a rotating magnetic field can cause a sputtering target 10 to develop a sputtering surface 12 having erosion grooves 14 and microcracks 16 that extend downward from the erosion grooves can also form, as shown in FIGS. 1A and 1B. The localized microcracks 16 which occur at the erosion grooves 14 can result in the ejection of sputtered particles during the sputtering process, which then deposit on the substrate to reduce yields. Sputtered particles that land on chamber components can also flake off at a later time due to thermal stresses arising from heating and cooling cycles.
Thus it is desirable to have a sputtering target capable of being more efficiently, and more uniformly, cooled by a target cooling system. It is also desirable for the target to exhibit reduced localized cracking from thermal stresses.